This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 9901794-9 filed in Sweden on May 18, 1999; the entire content of which is hereby incorporated by reference.
This invention relates to a loudspeaker assembly for use in electronic devices, comprising a loudspeaker for emitting sound through a front cover, and a board for mounting components, the board having a first side carrying user interface means accessible through the front plate, and a second side facing towards a back cover.
On the market for small-sized hand held electronic equipment especially mobile telephones, user friendliness is an extremely important parameter in the competition with other vendors of mobile telephones. The development of integrated circuit technology has made it possible to incorporate numerous functions which involve interaction with the user via a user interface. Typically, a user interface comprises relatively large components like a keypad and a display. In different types of electronic equipment, e.g. mobile telephones, a loudspeaker and/or a microphone is also incorporated in the electronic equipment.
When it is a requirement e.g. that it shall be possible to have access to all functions of the electronic device via a front cover, and that the overall size of the electronic equipment shall be small enough to be held and operated by one hand, the overall size of the electronic device constrains the size of the individual components i.e. the keypad, the display, etc. Thereby the display and the keypad get very small and inconvenient to use.
From a first type of marketed mobile telephones it is well-known to mount a loudspeaker on the back of a front cover and to connect the loudspeaker to a printed circuit board, PCB, by means of wires. However, this solution is inconvenient in that the speaker occupies much space at the backside of the front cover. This in turn limits the possible maximum size of other components accessible via the front cover. Moreover, such a mobile telephone is rather expensive to manufacture due to the task of mounting the electrical wires.
From a second type of marketed mobile telephones it is well-known to mount a loudspeaker on that side of a printed circuit board that faces towards the front cover. However, this solution is also inconvenient in that the speaker occupies much space at the backside of the front cover. Such mobile phones are also rather expensive to manufacture due to the task of mounting, involving soldering, the speaker on the surface of the printed circuit board.
Consequently, the prior art involves the problem that the loudspeaker occupies too much space at the backside of the front cover of an electronic device.
Thus an object of this invention is to provide a loud-speaker assembly which utilizes the space in electronic devices in a more convenient way.
This is achieved when the loudspeaker assembly mentioned in the opening paragraph is characterized in that the loudspeaker is mounted between the board and the back cover.
Consequently, the size and the position of other components such as a keypad and a display are riot constrained by the loudspeaker. Moreover, the front cover can be made free for electromechanical components. This may facilitate exchangeable front covers, since it is possible to manufacture cheaper front covers. Further, a designer of an electronic device comprising a loudspeaker assembly according to the invention is allowed to design with a larger degree of freedom.
When the board has an opening for transmission of sound, sound is transmitted from the loudspeaker to a listener/user.
In an expedient embodiment the loudspeaker assembly comprises a first resonance box including an opening through the front cover and an opening through the board and the first resonance box is otherwise closed.
When the loudspeaker assembly comprises a second resonance box which is coupled to the loudspeaker, including an opening through the board, and which is otherwise closed an additional resonance box is created and the high frequency response of the speaker assembly is enhanced. Consequently, it is possible to reduce the effect of the space surrounding the electronic device, e.g. the ear cavity of a listener, in the reproduction of sound. Further, it the loudspeaker assembly is placed close to a microphone operated in connection with the loudspeaker the resonance boxes may reduce or eliminate undesired acoustical feed-back from the loudspeaker to the micro phone.
This is possible in particular when the opening through the board connects the first and second resonance boxes.
In a particular expedient embodiment the first resonance box has a relatively small cross sectional area in a plane substantially parallel to the board compared to the cross sectional area, in a plane substantially parallel to the board, of the second resonance box. Thereby sound is transferred from the loudspeaker to the listener via two resonance boxes which can be designed for a specific sound transmission, while very little space is occupied on the back side of the front cover.
This is also possible when the first resonance box has a relatively small cross sectional area in a plane substantially parallel to the board compared to the diameter of the loudspeaker.
The loudspeaker may be attached to the second side of the board to form a resonance box between the board and the loudspeaker. Thereby only a minimum of effort is needed in mounting the speaker when high-volume production of electronic devices is considered.
Alternatively, the loudspeaker may be attached to the inner side of the back plate, the inner side facing towards the second side of the board. Hereby, it is possible to mount the speaker on the back cover independently of the process of mounting other components on the printed circuit board.
In an expedient embodiment a first side of the loudspeaker is coupled to the second resonance box and a second side of the loudspeaker is coupled to another volume by means of a sound channel. Thereby an additional design parameter is included.
When the loudspeaker is connected to the board by means of electrical connectors extending within the second resonance box a very compact and cost-effective solution for high-volume production is obtained.
Moreover, the invention relates to a mobile telephone comprising a loudspeaker assembly.